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GCN Circular 33633

IceCube-230416A: IceCube observation of a high-energy neutrino candidate
2023-04-16T12:53:20Z (a year ago)
Marcos Santander at U. Alabama/IceCube <>
The IceCube Collaboration ( reports:

On 2023-04-16 at 05:22:26.15 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.53 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection.

After the initial automated alert (, more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2023-04-16
Time: 05:22:26.15 UT
RA: 345.85 (+0.41 / -0.63 deg 90% PSF containment) J2000
Dec: +9.14 (+0.81 / -0.76 deg 90% PSF containment) J2000

We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No gamma-ray sources listed in the 4FGL-DR3 Fermi-LAT catalog is located within the 90% containment radius of the event. The nearest source is 4FGL J2306.6+0940 located at RA 346.65 deg, Dec +9.67 deg J2000, 0.95 deg away from the best-fit position.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at
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